The present invention relates to a process of producing hydrogen peroxide by direct reaction between hydrogen and oxygen in the presence of a catalyst, to form hydrogen peroxide gas, a new catalyst suitable for the process and preparation thereof.
Production of hydrogen peroxide by direct reaction between hydrogen and oxygen can be performed by contacting hydrogen and oxygen with a catalyst in an aqueous reaction medium as described in, for example, the U.S. Pat. Nos. 4,681,751, 4,772,458, 5,180,573, 5,128,114 and 5,338,531, as well as J. R. Kosak (DuPont), "A Novel Fixed Bed Catalyst for the Direct Combination of H.sub.2 and O.sub.2 to H.sub.2 O.sub.2 ", Chem. Ind. (Dekker), 1995, Vol. 62, Catalysis of Organic Reactions.
However, the formation of hydrogen peroxide is rather slow and it is hard to obtain high concentrations of hydrogen peroxide. These problems are assumed to be due to the facts that only low amounts of the reactants can be dissolved in the reaction medium and that the same catalyst that promotes formation of hydrogen peroxide also catalyses its decomposition into water and oxygen.
U.S. Pat. No. 5,500,202 discloses production of hydrogen peroxide in a reactor, wherein hydrogen and oxygen are reacted in a gaseous state at the surface of a solid catalyst and the hydrogen peroxide formed is dissolved in a liquid trickling through the reactor. However, also in this process only hydrogen peroxide solutions of low concentration and low purity can be obtained.
DE patent 558431 discloses production of hydrogen peroxide from oxygen and hydrogen in gas phase at a temperature below the freezing point and a pressure of at least 100 atm. These extreme conditions render the process very expensive commercially unattractive.
CH patent 140403 discloses a similar method but fails to suggest any suitable temperature, while U.S. Pat. No. 2,368,640 recommends operation at a temperature between 400 and 650.degree. C.
WO 97/32812 discloses production of hydrogen peroxide by contacting hydrogen and oxygen in gas phase with a catalyst at a temperature up to 100.degree. C. and a pressure up to 100 bar. Although it is possible to achieve a high reaction rate it has, however, been found that this process cannot readily be operated under stable conditions, particularly if it is desirable to obtain hydrogen peroxide at high concentration.